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Measurement of the He Ground State Lamb Shift Via the Two-Photon 11S - 21S transition



S Bergeson, A Balakrishnan, K G. Baldwin, Thomas B. Lucatorto, J P. Marangos, T J. McIlrath, Thomas R. O'Brian, S L. Rolston, J Wen, N Westbrook, C H. Cheng, E E. Eyler, Craig J. Sansonetti


We have extended two-photon Doppler-free spectroscopy to the vacuum ultraviolet spectral region to accurately measure the He 11S - 21S transition at 120 nm. Our result is 4 984 872 315[48] MHz. This yields a ground state Lamb shift of 41104[48] MHz, in fair agreement with theory and other experiments. This approach has the potential for significantly better accuracy once improvements in the laser and the wavelength metrology are implemented.
Physical Review Letters
No. 16


ground state, helium, Lamb shift, quantum electrodynamics, two-photon VUV spectroscopy


Bergeson, S. , Balakrishnan, A. , Baldwin, K. , Lucatorto, T. , Marangos, J. , McIlrath, T. , O'Brian, T. , Rolston, S. , Wen, J. , Westbrook, N. , Cheng, C. , Eyler, E. and Sansonetti, C. (1998), Measurement of the He Ground State Lamb Shift Via the Two-Photon 1<sup>1</sup>S - 2<sup>1</sup>S transition, Physical Review Letters (Accessed April 14, 2024)
Created April 1, 1998, Updated February 17, 2017